The higher the outdoor temperature, the higher the cooling load of a building. Especially in cities, the cooling load can be higher compared to the surrounding countryside because of higher temperatures by 2 to 3 degrees Celsius. Peak temperature differences can be even higher. The urban heat island effect is the reason for this phenomenon. The high concentration of dark surfaces with high heat capacities like roads and buildings absorbs much more solar radiation. Little greenery and no water bodies cause a lack of evapotranspiration which would have a cooling effect. Additionally, many forms of pollution like waste heat from industries, cars and air-conditioning systems are increasing the external temperature.

How to determine appropriate urban heat island mitigation strategies?

Peak temperatures of 45 °C (113 °F) or more during the summer season cause heavy cooling loads in the United Arab Emirates. In Abu Dhabi, about 60 percent of the annual energy expenses are caused by air-conditioning systems. It can even rise up to 75 percent on peak days. The urban heat island causes up to 15 percent of the emirate’s yearly cooling load in Abu Dhabi. Reducing the urban heat means cutting energy costs.

Researchers at MIT and the Masdar Institute are creating a three-dimensional urban microclimate model to investigate the impact of several urban heat island mitigation strategies

“The more cooling you have, the more heat air-conditioning systems release into the urban environment, which then elevates the ambient temperature and further increases the cooling demand. It’s a vicious cycle,” said Masdar Institute’s Afshin Afshari, professor of practice of engineering systems and management, who is a member of the Masdar Institute-MIT research team.

Scientists at Massachusetts Institute of Technology (MIT) and the Masdar Institute, a graduate-level technology university in the UAE, are searching for ways to reduce the urban heat island effect. The development of a new three-dimensional urban microclimate model for the downtown area of Abu Dhabi shall enable to investigate the impact of various strategies to mitigate the urban heat island. It could be a valuable urban planning decision-making tool. Influencing factors like geometric effects of buildings, materials, street layouts, green spaces, shading strategies, and water points can be taken into account.

“Very few research teams in the world approach the problem as an integrated phenomenon,” Afshari explained. “Most microclimatologists assume buildings are simple geometric obstacles with a constant temperature, and don’t look at the energy and heat the building produces, while building physicists are not interested in the urban climatology. But we see that the two phenomena are closely coupled and that their dissociation can lead to large modeling errors.”

According to MIT, the 3-D computational model shows the complex process of heat flows between buildings in Abu Dhabi’s downtown area. It is possible to conclude important climatic variables like air temperature, building façade temperatures, wind speed, solar radiation, and ground temperature.

The researchers considered local weather data, the accurate geographical city structure and other remote sensing data. They estimated the cooling demand of the buildings as well as the released heat from air-conditioning systems and integrated the climatic data, building data, and, to some degree, motorized traffic data. To get a clearer picture, more detailed information, and in order to improve the model, the researchers install dozens of in-house developed weather sensors in downtown area.

Urban heat island mitigation is an important component to reduce the country’s high energy costs and carbon footprint. An affordable way to optimize “Abu Dhabi’s smart infrastructure systems through a tool that enables city planners to design a cooler, more productive city, which will in turn increase the city’s competitiveness and prosperity.”

“The impact from this research project is spreading to the students we teach at both MI and MIT,” Norford said. “The broader and more important impact we hope our research achieves is on professional practice. If architects, developers, and planners use our software to evaluate alternative designs and make informed decisions to locate, design, and operate buildings in ways that minimize urban heat releases and improve the thermal comfort of urban dwellers, we will have achieved our goal.”

B-House provides more green power than needed

According to an announcement of Pomeroy Studio in January 2016, their completed B House has been awarded for the highest Singaporean award for environment‐friendly buildings, the Building Construction Authority’s (BCA) Green Mark Platinum Award. The modern carbon-negative domicile is highly efficient when it comes to waste, water and energy. A large polycrystalline photovoltaic system generates more electricity as needed. It is even possible to feed a surplus of solar electricity into the grid. Further passive design techniques and sophisticated technologies enable its residents to live in one of the most sustainable homes in Singapore.

Progress has been made since the Sime Darby Idea House (2010) in Malaysia. Allegedly, it was Asia’s first carbon‐zero prototype home. Pomeroy investigated the traditional Singaporean Black and White bungalow with the variable shutters, large roof overhangs and verandas for outdoor living and entertaining. Based on these insights like passive design techniques and space planning principles Pomeroy adapted B House to the climatic conditions of Singapore in order to reduce the demand of energy and water. Heat from the East and West sun is also minimized through the sophisticated orientation and shape. The off-site manufactured modules reduce wasteful off-­cuts as well as the building time by 50 percent as compared to a similar sized residential building.

“The owner of the B House was keen to push the boundaries of sustainable design for a private commission of two family bungalows in Bukit Timah, Singapore” said Founding Principal Prof. Jason Pomeroy, continuing “the home sought to ensure that the occupants would never have energy bills again, and greatly reduced water bills. The challenge therefore was to create a zero carbon house at the same cost of a bungalow comparable in scale. What started as a carbon zero project would eventually become a pioneering operational carbon negative house in Singapore”

“The future of sustainability is not just about technology, but, like the B House, draws on the essence of culture and tradition to create built environments that are carbon‐free and truly reflect their inhabitants’ way of life” said Pomeroy, …

… adding “We are delighted to have been given the opportunity to design this carbon negative home in Singapore. This project complements our Studio’s continued research into the field of zero­‐carbon development and its application to commercially orientated projects. We are proud to have been able to push the boundaries of sustainable design at the same price point as the ‘business as usual’, whilst retaining a commitment to the culture of place”.

Zero electrical resistance could save an inconceivable amount of energy, resources and expenditures

An enormous number of electrical systems like any kind of computers, switchboards, telecommunication devices or screens are in use in any city. The more inhabitants, the more energy-consuming appliances. It is known that electrical resistances of every electric device cause power dissipation in the form of heat. The aggregated losses of all devices in a city can be surprisingly high. And they are increasing in consideration of the needed energy for cooling devices like ventilators or air conditioning systems. Zero electrical resistance could save an inconceivable amount of energy but also resources and expenditures for cooling devices.

Electrical Resistance

The electrical resistance of an electric device or material measures the reduction of the electric current when flowing through it. The higher the resistance of a conductor, the higher the reduction of the electric current and the more electrical energy is needed to push current through this resistance. Depending on the quantity of electrical resistances, electrical energy is dissipated and transformed into heat. In some cases, this heating effect is desired, this for example when using an electric kettle. But this power dissipation is often an undesirable effect and causes lost energy, for example a warmed up notebook or TV. Warm server rooms even require additional energy for cooling devices. The reciprocal of the electrical resistance is the electrical conductivity – the capability to conduct an electrical current.

Zero electrical resistance through topological insulators and very thin materials

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Scientists at the US-basedMassachusetts Institute of Technology (MIT) are also interested in materials and devices with low or better zero electrical resistance. It can reduce energy losses but also extend device capabilities. In recent years, researchers tried to make progress by using very thin materials and topological insulators (TIs). A topological insulator behaves like an insulator in its interior in contrast to its surface which conducts electricity. Electrons are only able to move along the surface of the material.

According to MIT, a breakthrough towards the dissipationless goal has been achieved when the current enters a quantum state without any external magnetic fields at extremely low temperatures. The potential could be enormous if the restriction of the low temperature can be eliminated. MIT postdoc Cui-Zu Chang, then a doctoral student at Tsinghua University in China, and colleagues at Chinese Academy of Sciences-Institute of Physics, Tsinghua, and Stanford University demonstrated a system with remnants of electrical resistance and very close to zero electrical resistance.

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Chang and colleagues at MIT were using vanadium instead of chromium for thinner atomic layers for the magnetic topological insulator. With further optimizations, Chang and colleagues at MIT and Penn State University achieved zero electrical resistance at the edge of a sample with extremely low temperatures of 0.025 kelvins. They also stacked sample films on a base of strontium titanate. The results are published inNature Materials in May 2015.

“A signal entering this system can propagate a long distance without losing any of its energy. While presently it can only be realized at very low temperatures, there are indications that this can be raised,” Chang says.

Chang and colleagues continue their research, for example, by experimenting with different materials. It is called doping if an extra element like chromium or vanadium is added to the material. Compared with chromium, vanadium has three advantages. It is possible to operate at zero resistance at a slightly higher but still very cold temperature. The stability of its intrinsic magnetism can be increased tenfold and it is possible to halve the carrier density.

It is still a long way. However, the practical implementation is a further building block for future green cities.

Approximately 55 percent of community-wide emissions in 2010 are contributed by the transportation system

The major city in California is set to become the largest city in the United States to run on 100 percent renewable energy according to a recent speech of the mayor Kevin Faulconer. It is seen as a job motor and a key driver for the reduction of the city’s greenhouse gas emissions. Solar energy is a key element and will help to achieve this ambitious target. Already the former governor Arnold Schwarzenegger announced the 2050 greenhouse gas (GHG) reduction target of 80 percent compared to the year 1990 for the entire state of California.

According to the 74-page Climate Action Plan of San Diego, concordantly approved in December 2015, the city is a leader in innovation and sustainability and takes the lead in California to tackle climate change. Several facts justify this claim.

According to the state environmental group Environment California, solar installations have grown 76.6 percent in two years in San Diego. It is the city with the second-highest number of solar panels in the United States, just behind Los Angeles. According to Nicole Capretz, executive director of the Climate Action Campaign, rooftop solar will contribute about 20 percent of the ‘100 percent renewable energy goal’. Researchers claim that San Diego had enough solar capacity at the end of 2015 to power about 47,000 homes. Ranking 4th behind Honolulu, Indianapolis and San Jose, San Diego also scored well on a solar-per-person basis.

Generally, renewable energies play a decisive role to achieve the GHG reduction targets. A combination of on-site generation and large-scale renewables is planned to assist the City in meeting its ambitious targets in an efficient way. San Diego’s fortunate geographical position and many hours of sun are customized conditions for solar power systems. A crucial advantage for the switch to 100 percent renewable energies. The City also has photovoltaics systems installed at various facilities. Approximately 2.2 MW of renewable energy is provided by photovoltaic plants at water treatment plants. The new 3.3 MW solar panel system in front of San Diego’s International Airport is expected to save up to $8 million in energy costs over the next 20 years.

100 percent renewables are not the only option in order to reduce harmful emissions. Five bold strategies have been identified to reduce GHG emissions in San Diego to achieve the 2035 targets:

Approximately 55 percent of community-wide emissions in 2010 are contributed by the transportation system. For this reason, transportation strategies cover a broad range of activities with the objective to reduce vehicle miles traveled, improve mobility, and enhance the fuel efficiency of vehicles. Individual transposition measures involve, for example, changing land uses, promoting alternative travel modes, revising parking standards, and managing parking. San Diego intends to make about 50 percent of its vehicles electric.

The decomposition by-product of organic material – methane – has a warming impact which is twenty times higher than carbon dioxide. Because of this, San Diego aims to achieve a 75 percent waste diversion rate by 2020. The City also strives for the Zero Waste disposal by 2040. It is already possible to generate nearly 15 MW renewable energy with methane from landfills. Furthermore, the Point Loma Wastewater Treatment Plant is able to produce green gas and inject it into the natural gas pipeline.

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Additionally, it is planned to increase the city’s tree canopy cover to 35 percent. The advantages are clear: A reduced Urban Heat Island effect, the enhanced ability to absorb carbon dioxides, providing cool and shaded places, and a greener city scape are significant benefits in the hot city adjacent to the border with Mexico.

Hyperions is an extraordinary and futuristic but not unrealistic vision and can be seen as a vertical village

Indian agroecologist Amlankusum and Paris-based Vincent Callebaut Architectures have an extraordinary and futuristic but not unrealistic vision. It is called Hyperions. The set of six 36-story towers or rather ‘vertical farms’, each 128 meters tall, is connected by common green spaces and walkways. This green vision is set to be completed in by 2022 near New Delhi, India.

The vertical eco-neighborhood called Hyperions produces more energy than it consumes

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The six garden towers can be seen as a vertical village with a high social, cultural and use mix. The flexible, evolutionary spaces dedicated to business incubators, living labs, coworking spaces, multi-purpose rooms and concierge services are located behind the solar facades.

The apartments, as well as student housing, open onto cascading hydroponic balconies. The furnishings are made of natural materials such as sandalwood and tamarind. They are provided by local recycling shops, cabinetmakers and fab labs.

The towers of Hyperions are built with cross-laminated timber and are covered with orchard gardens

The various spatial uses are linked together with footbridges, and converge under a large orchard roof that serves as a meeting place for our small urban farmer community (Amlankusum, Agroecologist, Jaypee | Vincent Callebaut Architectures, Paris)

The façades of the towers are wrapped by blue-colored, photovoltaic and thermal scales. They are able to follow the sun from East to West. In this way, it is possible to produce hot water and artificial lighting for Hyperion. It is intended to recharge the electric vehicles in real time by the solar façades.

Allegedly, all the wood required to build the garden towers comes from a Delhi forest, which is also managed sustainably. The wood is collected with respect for the appropriate cutting cycle and regenerating capacity (Amlankusum, Agroecologist, Jaypee | Vincent Callebaut Architectures, Paris)

Producing wooden materials requires less energy and is less polluting than standard materials like steel or concrete. By substituting these materials with wood, it is possible to avoid the emission of up to 1.1 tons of carbon dioxide per cubic meter. Between its CO₂-sequestrating capacity during its growth phase and its low-emission manufacturing processes, one cubic meter of wood is able to save two tons of carbon dioxide.

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Amlankusum outlines, “As for me, as an agroecologist, I suggested that the project be covered with a genuine, virtuous feeding ecosystem based on organic aquaponics. Thus, carrots, tomatoes, spinach, saffron and coriander grow in light substrates made of clay balls on each apartment’s balcony and in hydroponic greenhouses. They are irrigated with water from ponds breeding several species of fish, whose excrement is naturally rich in nitrogen, phosphorus and potassium. In these organic fish farms promoting mixed farming, we also find mollusks and crustaceans filtering and grazing the organic micro-waste. This vertical farming gives residents some food autonomy while saving on the land. Our food is produced mostly on-site or in neighboring agroforestry fields. We also manage to save up to 90% of our water needs, since it circulates in a closed loop via small pumped hydroelectric energy storage (PHES) plants.”

“We the “Urban Farmers” claim that converting worldwide agriculture into organic techniques and bio-sourced construction could reduce worldwide CO2 emissions by about 40% by 2030. Hyperions is a sustainable agro-ecosystem project capable of resisting climate change thanks to its healthy economic and environmental ecosystems.”, he adds.